You have all heard about the DNA double helix and genes. Many of you know that mutations occur randomly, that the DNA sequence is read by successive groups of three bases (the codons), that many genes encode enzymes, and that gene expression can be regulated.
These concepts were proposed on the basis of astute genetic experiments, as well as often on biochemical results. The original articles were these concepts appeared are however not frequently part of the normal curriculum of biologists, biochemists and medical students.
This course proposes to read study and discuss a small selection of these classical papers, and to put these landmarks in their historical context. Most of the authors displayed interesting personal histories and many of their contributions go beyond not only the papers we will read but probably all their scientific papers.
Our understanding of the scientific process, of the philosophy underlying the process of scientific discovery, and on the integration of new concepts is not only important for the history of science but also for the mental development of creative science.

À partir de la leçon

Session 4

When DNA was found to be the genetic material, it was not known how this molecule could carry information. The structure of DNA thus became of critical importance. The available X-ray images obtained by M. Wilkins and R. Franklin only yielded a rough picture, and even R. Franklin, who had the clearest diffraction data, could not decide whether the molecules contained two or three strands. Both Pauling and Watson and Crick used molecular models with known inter-nuclear distances (bond length) and bond angles to predict a structure. While the model of Pauling was hardly realistic, since it used the protonated form of the phosphate, the model proposed by Watson and Crick proposed that DNA consists of a pair of DNA strands. Furthermore, it indicated that any nucleotide sequence could be accommodated in the structure. The only central biological issue that was addressed in the first paper was replication, and the famous sentence was really nothing more than a priority claim. Much more biology was discussed in the second paper. It was assumed that base pairing is sufficient to account for the fidelity of replication. The importance of DNA polymerase in replication fidelity was first demonstrated by Speyer.